Upgrade to 1.4

Minor BC Break: Doctrine\Common\Cache\FileCache#$extension is now private.

If you need to override the value of Doctrine\Common\Cache\FileCache#$extension, then use the
second parameter of Doctrine\Common\Cache\FileCache#__construct() instead of overriding
the property in your own implementation.

Minor BC Break: file based caches paths changed

Doctrine\Common\Cache\FileCache, Doctrine\Common\Cache\PhpFileCache and
Doctrine\Common\Cache\FilesystemCache are using a different cache paths structure.

If you rely on warmed up caches for deployments, consider that caches generated
with doctrine/cache <1.4 are not compatible with the new directory structure,
and will be ignored.